Pneumatic hand tool valve and trigger lock



Nov. 18, 1952 F. P. FORSS PNEUMATIC HAND TOOL VALVE AND TRIGGER LOCK Filed Occ. 2, 1946 jrzzf/u offjv/zss Patented Nov. 18, 1952 PNEUMIATIC HAND TOOL VALVE AND TRIGGER LOCK Frithiof P. Forss, Aurora, 111., assignor to Skilsaw, Inc., Chicago, 111., a corporation of Delaware Application October 2, 1946, Serial No. 700,664

12 Claims. 1

This application is a division of my co-pending application Serial No. 618,047, filed September 22, 1945, now Patent No. 2,545,453, issued March 20, 1951.

This invention relates to pneumatic tools and more particularly small, light weight, high-speed hand, tools such as are designed for use in die grinding and rotary filing.

The principal object is to provide a simple and reliable safety lock for the throttle valve which permits locking the trigger either in the On or off position, locking in the on position facilitating working with the tool by relieving the operator of the necessity of holding the trigger down, and locking in the off position avoiding the danger of the spindle being accidentally started when the tool is laid down or when a wheel or other tool is being removed from or applied to the spindle.

The invention is illustrated in the accompanying drawing, in which Fig. 1 is a side view of a pneumatic hand tool, one end portion of which is shown in longitudinal section to show the trigger in connection with which the locking means of my invention is provided;

Fig. 2 is an enlarged sectional detail taken on the line 22 of Fig. 1;

Fig. 3 is an end view of the tool showing the lock portion in cross section on line 3-3 of Fig. l, and

Figs. 4 and 5 are respectively a plan view and edge view of the latch slide, shown actual size.

The same reference numerals are applied to corresponding parts throughout the views.

The present tool has been designed for use as a die grinder for finishing and similar work, and as a rotary file for cleaning aluminum castings and other work of the same nature as, for' example, metal pattern work, and also as a tool post grinder for internal grinding. The tool is, however, adaptable to various other uses.

Referring mainly to Fig. l, the reference numeral I designates the housing which has a center opening 8 in its end wall 9 through which the rotary spindle I0 projects. H is a chuck threaded on the end of the spindle and having a flexible sleeve collet to clamp various sized shanks on grinding wheels, rotary files and other tools.

Forming one end of the housing is a head 23 that is threaded into the open end of the housing 1, as indicated at 24, and has a nipple 25 threaded into the outer end thereof for connection of a flexible air hose to the tool for delivery of compressed air thereto. A valve bushing 26 has a press fit in a diametrically extending hole 27 in the head 23 and contains a stainless steel ball valve 28 which is normally held against a seat 29 in the bushing by means of a coiled compression spring 30. The valve 28 may be unseated by endwise movement of a pin or plunger 3] slidable with a close working fit in a center hole 32 provided in the end of the bushing 26, the pin being riveted or otherwise suitably secured to a trigger 33 which is disposed in parallel relation to the longitudinal axis of the tool and has a plunger 34 riveted or otherwise suitably secured to its other end and slidable in a radial bore 35 provided in the head 23. A spring 36 acting between the inner end of the bore 35 and the plunger 34 tends normally to hold the trigger 33 and pin 3| in the retracted or "off position, and inasmuch as the pin 3| is subjected to end thrust by the spring 30 in the closing of the valve 28 it is clear that the joint action of the two springs 30 and 36, which preferably offer substantially the same resistance to compression, eliminates likelihood of any binding action in the operation of the trigger. The trigger can be locked in either extreme position, that is to say, in on or off position, by means of a latch slide 33', as hereinafter described. The air admitted through the nipple 25 flows through a passage 38 into the bushing 26 below the valve 28, and if the valve 28 is opened the air flows through the bushing and through two passages 39 in the head 23 into an annular groove in the inner end of the head. From this groove the air flows through suitable passages into the air intake chamber of the rotary pneumatic motor in housing I, the rotor of which drives the spindle Ill. The compressed air expends its force on the rotor and is exhausted as described in the parent application above identified.

Referring now to Figs. 2 to 5, I shall describe the safety lock for the trigger 33 prov ded in accordance with my invention for locking the trigger either in the on or off position. When the trigger is locked in the off position, the motor cannot be started accidentally by being laid down or in the handling of the tool while removing a grinding wheel or other tool from the spindle. The latch slide 31, mentioned previously, is made of fiat spring steel arched on a smaller radius than the radius of the head 23, so that when it is cramped in the shallow guideway 40 provided therefor in the plate 4|, sufilcient frictional resistance is assured by its contact at both ends on the head and between the ends on' the plate 4! to eliminate likelihood of the slide being moved endwise accidentally. The plate 4| is fastened by three screws 42 onto a flat face provided on one side of the head 23. The plate 4| has a hole 43 through which the reduced upper end of the plunger 34 is freely slidable and it serves also to retain the plunger 34 by engagement with the enlarged lower end portion that operates in the hole 35. The guide groove cuts through one side of the hole 43,

as clearly appears in Fig. 2. The slide 3! has bent-up end portions 44 which are easily accessible to the operator on opposite sides of the trigger 33, as thumb pieces, to move the slide in either direction to lock or unlock the trigger. A notch 45 is provided in the slide 31, and in the unlocked position of the slide permits free movement of the plunger 34 up and down relative to the slide 31. However, there are two slots 45 cut into one side of the reduced upper end portion of the plunger 34, as clearly appears in Fig. 1, and when the slide 3'l is moved endwise from the unlocked position, shown in full lines in Fig. 2, to the locked position, indicated in dotted lines in the same figure, it will engage in whichever slot 46 is in coplanar relation to the slide. Hence, the plunger 34 may be locked in either its normal retracted position, shown in Fig. l, which corresponds to the off position for the valve 28, or in its depressed position, which corresponds to the on or open position of the valve 28.

It is believed the foregoing description conveys a good understanding of the objects and advantages of my invention. The appended claims have been drawn to cover all legitimate modifications and adaptations.

I claim:

1. In a trigger controlled hand tool, comprising a housing, the combination of a reciprocable trigger operable plunger element projecting from said housing and having a transverse slot provided therein, and a slide made of wide fiat spring material guided in a wide but relatively shallow guideway provided therefor on said housing for movement manually transversely relative to said plunger and arranged to enter said slot to lock the plunger against movement and having a notch provided in one longitudinal edge portion which in a certain position of the slide receives the plunger and permits free movement thereof, said slide being normally arched endwise between the opposite ends thereof and being retained in fiattened condition in the aforesaid shallow guideway so that it exerts a frictional drag by sliding contact at its ends and at an intermediate point where it engages the guideway, so as to be held by friction in either of its adjusted positions until moved manually to another position.

2. A tool as set forth in claim 1, wherein said plunger has at least one additional transverse slot provided therein in spaced parallel relation to the first mentioned transverse slot, either of said slots being adapted to receive said slide to lock the trigger in any one of a plurality of positions.

3.- As an article of manufacture, a trigger latch slide of the character described comprising a generally rectangular thin sheet metal body having a notch provided in one of the longitudinal edge portions and having upwardly bent end portions in substantially parallel relation, the body being of spring material and being normally arched'endwise between the upwardly bent end por ons.

4;, In a trigger mechanism of the character described, a body in which are guided for endwise movement two parallel plunger parts, an elongated trigger element in transverse relation to said plunger parts and secured to the outer ends thereof so as to be guided thereby for reciprocation relative to the body, one of the plungers having a reduced outer end portion, a plate secured to the body and having the reduced portion of the one plunger guided in a hole provided therein, said plate having a wide but relatively shallow transverse groove provided on the inner side intersecting one side of said hole, the reduced portion of said plunger having at least one transverse slot provided therein parallel to the plate, and a slide operable back and forth in said groove and enterable manually in said slot but having also a notch therein which in a certain position of said slide receives the reduced portion of said plunger and permits free reciprocatory movement thereof.

5. A trigger mechanism as set forth in claim 4, wherein said slide is of thin flat spring material of less thickness than the depth of the groove in the plate and wherein said slide is normally arched endwise to such an extent that it i flattened in the cramping thereof in said shallow groove whereby it exerts a frictional drag by sliding contact at itsends and at an intermediate point where it engages the body and plate in the assembled position of the slide.

6. In a trigger mechanism of the character described, a body in which are guided for endwise movement two parallel plunger parts, springs operatively associated with said plunger parts to resist inward movement thereof substantially equally, an elongated trigger element in transverse relation to said plunger parts and secured to the outer ends thereof so as to be guided thereby for reciprocation relative to the body,-one of said plunger parts having a plurality of parallel slots provided therein transversely thereof, and manually operable latch means on the body selectively enterable in either of said slots to lock the trigger in any one of a plurality of positions.

'7. In a trigger mechanism of the character described, a body in which are guided for endwise movement two parallel plunger parts, a valve operable by one of said plunger parts to closed or open position, springs operatively associated with said plunger parts to resist inward movement thereof substantially equally, an elongated trigger element in transverse relation to said plunger parts and secured to the outer ends thereof so as to be guided thereby for reciprocation relative to the body, one of said plunger parts having two parallel slots provided therein transversely thereof, and manually operable latch means on the body enterable in said slots seleczively to lock the trigger in open or closed posiion.

8. In a trigger mechanism of the character described, a body in which are guided for endwise movement two parallel plunger parts, springs operatively associated with said plunger parts to resist inward movement thereof substantially equally, an elongated trigger element in transverse relation to said plunger parts and secured to the outer ends thereof so as to be guided thereby for reciprocation relative to the body, one of said plunger parts having a slot provided therein transversely thereof, and a slide guided on said body for movement transversely relative to the one part arranged to enter said slot to lock the trigger against movement from a predetermined position and having, a notch provided therein which in a certain position of the slide receives and permits reciprocatory movement of said one part to permit free movement of the trigger.

9. In a trigger mechanism of the character described, a body in which are guided for endwise movement two parallel plunger parts, springs operatively associated with said plunger parts to resist inward movement thereof substantially equally, an elongated trigger element in transverse relation to said plunger parts and secured to the outer ends thereof so as to be guided thereby for reciprocation relative to the body, one of said plunger parts having a plurality of parallel slots provided therein transversely thereof, and a slide guided on said body for movement manually transversely relative to the one part arranged to enter said slots selectively to lock the trigger in any one of a plurality of positions and having a notch provided therein which in a certain position of the slide receives and permits re- L ciprocatory movement of said one part to permit free movement of the trigger.

10. In a trigger mechanism of the character described, a body in which is guided for endwise movement a plunger part, a trigger element fixed in transverse relation to the outer end of said plunger part for reciprocation thereof, the plunger having a reduced outer end portion, a plate secured to the body and having the reduced portion of the one plunger guided in a hole provided therein, said plate having a wide but relatively shallow transverse groove provided on the inner side intersecting one side of said hole, the reduced portion of said plunger having at least one transverse slot provided therein parallel to the plate, and a slide operable back and forth in said groove and enterable manually in said slot but having also a notch therein which in a certain position of said slide receives the reduced portion of said plunger and permits free reciprocatory movement thereof.

11. A trigger mechanism as set forth in claim 10, wherein said slide is of thin flat spring material of less thickness than the depth of the groove in the plate and wherein said slide is normally arched endwise to such an extent that it is flattened in the cramping thereof in said shallow groove whereby it exerts a frictional drag by sliding contact at its ends and at an intermediate point where it engages the body and plate in the assembled position of the slide.

12. In a trigger mechanism of the character described, a body in which are guided for endwise movement two parallel plunger parts, springs operatively associated with said plunger parts to resist inward movement thereof substantially equally, an elongated trigger element in transverse relation to said plunger parts and secured to the outer ends thereof so as to be guided thereby for reciprocation relative to the body, one of said plunger parts having a slot provided therein transversely thereof, and manually operable latch means on the body arranged to enter the slot to lock the trigger in a predetermined position.

FRITHIOF P. FORSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 605,049 Nicholsburg May 31, 1898 1,825,864 Harter Oct. 6, 1931 2,374,019 Kahler Apr. 17, 1945 FOREIGN PATENTS Number Country Date 34,218 Switzerland of 1905 200,334 Switzerland of 1938 274,578 Germany of 1914 

